Electron Impact Excitation and Dielectronic Recombination of Highly Charged Tungsten Ions

Abstract

Electron impact excitation (EIE) and dielectronic recombination (DR) of tungsten ions are basic atomic processes in nuclear fusion plasmas of the International Thermonuclear Experimental Reactor (ITER) tokamak. Detailed investigation of such processes is essential for modeling and diagnosing future fusion experiments performed on the ITER. In the present work, we studied total and partial electron-impact excitation (EIE) and DR cross-sections of highly charged tungsten ions by using the multiconfiguration Dirac-Fock method. The degrees of linear polarization of the subsequent X-ray emissions from unequally-populated magnetic sub-levels of these ions were estimated. It is found that the degrees of linear polarization of the same transition lines, but populated respectively by the EIE and DR processes, are very different, which makes diagnosis of the formation mechanism of X-ray emissions possible. In addition, with the help of the flexible atomic code on the basis of the relativistic configuration interaction method, DR rate coefficients of highly charged W 37+ to W 46+ ions are also studied, because of the importance in the ionization equilibrium of tungsten plasmas under running conditions of the ITER.

Dielectronic recombination of the open 4d-shell of tungsten: W37+–W28+

“…Relatively good agreement was seen between the present work, and the calculations performed by Ballance et al [49] for 39-like, and Li et al [25] for 45-and 46-like at peak abundance temperature. Very poor agreement was seen between the present work, and the calculations performed by Wu et al [51] and Safronova et al [16]. Unfortunately, it has still not been possible to pin down the reason for the difference between our calculations and Safronova et al's.…”

Radiative transitions for three lowest configurations of tungsten ions W38+–W43+

“…The theoretical and experimental studies of the tungsten ions are important in fusion plasma research, but available spectroscopic data for the ions with an open 4p N shell are incomplete. The basic atomic processes in tungsten ions W 37+ -W 46+ have been investigated using the relativistic methods in [4]. Our earlier studies of the highly-charged tungsten ions (see, e.g.…”

Comparision of Statistical Models for Calculations of Heavy Impurity Dielectronic Recombination Rates in Thermonuclear Fusion Plasmas

“…1-3 представлено сравнение результатов расчётов скорости диэлектронной рекомбинации по статистическим моделям (11) и (12), а также сравнение с данными квантово-механических расчётов кодами HULLAC [11] и FAC [12], учитывающих точную структуру атомных уровней. Как видно на ри-сунках, модели не сильно расходятся друг с другом и дают хорошее совпадение с квантово-механическими расчётами.…”